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571.
Bio-oil from pyrolysis of biomass is an important renewable source for liquid fuel and/or for chemicals. However, the application of bio-oil was severely restricted due to its high viscosity, acidity, and low heating value. Hence, it is necessary to upgrade the bio-oil for deoxygenation or for chemicals by catalytic reactions. In this paper, the catalytic behaviors of SAPO-34, ZSM-5, and Y zeolite on pyrolysis of cellulose were investigated via pyrolyzer combined with gas chromatography and mass spectrometer (Py-GC/MS) method in Py-mode. The results showed that ZSM-5 and Y zeolite could promote the conversions of oxygen-containing components to gases, water, aromatics, and phenols. Comparatively, more gas and water were generated under the catalysis of Y zeolite at lower temperatures, while at temperatures above 700°C, the effect of ZSM-5 became more distinct; aromatics were more generated under the catalysis of ZSM-5, while Y zeolite exerted a more distinct role in promoting the formation of phenols. The effect of SAPO-34 caused more water and furfural derivatives, less aromatics and phenols, and exerted a weak influence on gases. 相似文献
572.
573.
Emission factors for PCDD/PCDF determined from open combustion are used to estimate national emission budgets; therefore, it is important to have confidence in their accuracy. It has been suspected that artefacts may form due to the presence of hot metal surfaces of sampling equipment, thus skewing emission factors. In this study, emissions of PCDD/PCDF from open burning of forest biomass over a brick hearth were sampled. Five experiments were carried out using a portable sampler. Experiments were designed where the key variable, sample hood and inlet temperatures were manipulated. Other variables such as fuel origin, type and density were consistent. The measured concentration of PCDD/PCDF in the smoke samples ranged from 0.01 μg TEQ (t fuel)−1 at the lowest maximum hood temperature (185 °C) to 15 μg TEQ (t fuel)−1 at the highest maximum hood temperature (598 °C). when hood inlet temperatures exceeded 400 °C emission factors were significantly elevated and this is attributed to the formation of artefacts that can cause the over estimation of emission factors. The increase in hood temperature also resulted in a change in the PCDD/PCDF congener and homologue profile of the emissions. For example at the lowest temperature (Fire 1) the PCDD/PCDF ratio measured was 50:1, whereas at the highest temperature (Fire 5) this ratio was about 0.53:1. When the sampler hood and inlet temperatures were kept in the normal operating range of <200 °C, emission factors were comparable to those observed in many previous studies in Australia with emissions dominated by PCDD. 相似文献
574.
575.
开发区外场中距离大气扩散模式对城区影响研究 总被引:3,自引:2,他引:1
《中华人民共和国环境影响评价法》中提出了对规划 (含开发区 )要进行环境影响评价 ,而开发区建设大多在城市近郊 ,与城区一般相距十几公里以上 ,大气环境影响评价中属中距离范围。本文分析了在复杂地形条件下中距离大气扩散模式的计算方法及其对城区的影响。 相似文献
576.
烟尘、汽车尾气颗粒物中有机质的成分特征 总被引:1,自引:0,他引:1
通过对烟尘、汽车尾气排放颗粒物、尘土中的有机质经提取分离得饱和烃、芳香烃、菲烃、沥青四个馏分.四个溜分的相对含量有一定的差异性.并将其饱和烃、芳香烃,经GC-MS分析,其特征明显不同.这种特征的不同可算得大气颗粒物中有机污染的来源. 相似文献
577.
Estimation of Polish cigarettes contamination with cadmium and lead, and exposure to these metals via smoking 总被引:2,自引:0,他引:2
Galazyn-Sidorczuk M Brzóska MM Moniuszko-Jakoniuk J 《Environmental monitoring and assessment》2008,137(1-3):481-493
To estimate exposure to cadmium (Cd) and lead (Pb) through cigarette smoking, the concentrations of both metals in the blood
or/and urine of smokers (20 cigarettes or more per day for 10 years or longer) and their non-smoking counterparts inhabiting
an environmentally unpolluted area (Bialystok, Poland) were evaluated, as well as Cd and Pb contents in the cigarette brands
(produced in Poland) smoked by the participants, including intact cigarettes, pre-smoking (tobacco, paper and filter) and
post-smoking (butt, ash and smoke) cigarette components. Blood and urinary Cd concentrations in the smokers have been already
reported by us to be 2–4 times higher than in the non-smokers (Galażyn-Sidorczuk et al. Polish Journal of Environmental Studies,
13 (Suppl.1):91–95, 2004). All the other measurements are the subject of the present paper. Pb concentration in the blood of the cigarette smokers
(52.12 ± 15.51 μg l−1) was higher by 29% than in the non-smokers (40.42 ± 11.19 μg l−1). The mean Cd and Pb contents in the cigarettes were 0.6801 ± 0.1765 and 0.6853 ± 0.0746 μg per cigarette, respectively.
Under cigarette burning, performed using a machine for self-acting burning, on average 33% of Cd and 11% of Pb present in
the whole cigarette was released into the smoke. For Cd, unlike Pb, there was a high positive correlation between the metal
content in cigarettes and tobacco and its release into the smoke. Moreover, the subjects smoking cigarettes containing the
highest Cd amount had higher blood Cd concentration than smokers of other cigarette brands. The results give clear evidence
that in the case of inhabitants of areas unpolluted with Cd and Pb habitual cigarette smoking, due to tobacco contamination,
creates a serious source of chronic exposure to these metals, especially to Cd. 相似文献
578.
有风条件下火灾自然排烟的临界失效风速分析 总被引:1,自引:0,他引:1
采用双区模拟思想对有风条件下室内火灾自然补气、自然排烟过程进行分析。引入"总风压系数"和"临界失效风速"的概念,并将其作为评价外界环境风对自然排烟过程影响程度的判定参数。总风压系数非负时,外界风的存在将提高自然排烟的效果;总风压系数为负时,外界风的存在将降低自然排烟的效果,甚至使自然排烟失效。通过对排烟口内外压差以及气体流动进行分析,发现临界失效风速正比于总风压系数绝对值的-1/2次幂,并给出了不同条件下自然排烟临界失效风速的计算方法。实际采用自然排烟方式进行火灾排烟时,应尽量避免出现总风压系数为负的情形,以防止自然排烟的失效。 相似文献
579.
活塞风对地铁隧道内烟气扩散特性影响的数值模拟 总被引:2,自引:0,他引:2
研究目的是探索地铁列车活塞运动所造成的隧道内三维非均匀初场对列车火灾烟气扩散特性的影响。采用计算流体力学(CFD)方法模拟列车从运动到停止于隧道中的过程,通过将瞬时计算域内三维速度场经过数据转换和传递作为进一步模拟火灾烟气扩散过程的初始条件,检验有效疏散时间内列车附近疏散空间的安全性,并将模拟结果与静止初始条件下的模拟结果进行对比。模拟所采用的三维非均匀初场更接近于真实的物理过程,使模拟结果更有助于揭示实际火灾过程的本质。模拟结果显示列车运动所造成的惯性气流对火灾早期烟气扩散有显著的影响,所采用的研究方法和结论能为制定更加可靠和安全的火灾应急预案提供理论依据。 相似文献
580.